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Additionally, the soil in Nee Soon freshwater swamp forest is anaerobic and unstable 
due to periodic flooding (Nguyen et al., 2018). All these factors have resulted in a 
diverse flora and fauna that are adapted to these unusual conditions. However, it also 
means that these habitat specialists are sensitive to environmental disturbances such as 
changes in the drainage system, introduction of non-indigenous species, soil erosion, 
and disturbances from development (Ng & Lim, 1992; Yeo & Chia, 2010). 
Odonates (Order: Odonata) are of increasing applied research interest as 
potential biological indicators and tools for ecological modelling (Bried & Samways, 
2015). They are relatively well known taxonomically and the adults are easy to identify 
(Simaika & Samways, 2012; Kutcher & Bried, 2014). Hence they are good ecological 
indicators for the assessment of aquatic environments, especially for wetland and stream 
quality as they occupy the interface between aquatic and terrestrial ecosystems and are 
highly sensitive to environmental changes (Carvalho et al., 2013; Monteiro-Junior et 
al., 2013; Oliveira-Junior et al., 2015). There is also a major division within the order 
in terms of the ecophysiological requirements of different species (De Marco et al., 
2015). Members of the sub-order Anisoptera (dragonflies) are more useful indicators 
of degraded environments because they have more efficient homeostatic mechanisms 
and are more mobile, enabling them to tolerate a wider range of environmental 
conditions. By contrast, members of the sub-order Zygoptera (damselflies) tend to 
provide a more useful role as indicators of more preserved environments and higher 
levels of environmental heterogeneity because of their smaller body sizes, home 
ranges and greater ecophysiological restrictions (Oliveira-Junior et al., 2015). The 
structure of odonate communities can shift predictably in response to changes in local 
enviromuental conditions (Corbet, 1999; Juen et al., 2007; Juen & De Marco, 2011; 
Luke et al., 2017). 
To date most studies of odonates in Singapore have been taxonomic accounts. 
There is very little available data on their distribution and abundance in Nee Soon 
freshwater swamp forest. Murphy (1997) reported Odonata biodiversity in the nature 
reserves of Singapore by comprehensively reviewing the historical account and 
providing a list of species found in Singapore. He briefly discussed the distribution and 
habitat preferences for some of species and, from his list, only 15 species were specified 
as occurring within the location of Nee Soon, of which eight species were confined to 
Nee Soon freshwater swamp forest (other widely distributed species might have been 
found there without being mentioned specifically) Norma-Rashid et al. (2008) updated 
the list of dragonflies in Singapore, and identified 35 more species from Nee Soon. 
Tang et al. (2010) further updated the list, with 17 more species occurring at Nee Soon. 
Cheong et al. (2009) and Dow & Ngiam (2011) added two more species for Nee Soon. 
Munirah (2013) conducted a biodiversity assessment of Nee Soon freshwater swamp 
forest aquatic insects and recorded 15 species of larvae from eight odonate families. 
In this study, we aim to establish the most up-to-date knowledge on odonate 
diversity for Nee Soon freshwater swamp forest with an emphasis on abundance. 
The study may be read in conjunction with the sampling of aquatic insects by Su 
(2016) and aquatic macroinvertebrates (including odonate larvae) by Ho et al. (2018) 
concurrent with our study. We also investigate any distinct spatial distribution within 
